Diaphragm pump, particularly for dosing liquids

Abstract

In the case of a diaphragm pump, as is more particularly used for dosing or metering liquids and which is provided on the one hand with a dosing chamber with a suction and pressure valve and on the other with a hydraulic working chamber with drive piston and pressure relief valve, both chambers being separated by the working diaphragm, an effective diaphragm protection against excessive deflection and consequently overstressing is obtained in that the diaphragm defines a chamber connected to the working chamber by means of at least one overflow channel and in the vicinity of the overflow channel is guided a valve unit comprising a tappet with in each case one valve disk for the facing openings of the overflow channel and which is in operative connection with the diaphragm.

What is claimed is: 
     
       1. A diaphragm pump, particularly for dosing liquid, comprising a diaphragm arranged in a housing, a dosing chamber with a suction and a pressure valve on one side of the diaphragm, a hydraulic working chamber with a drive piston and a pressure relief valve on the other side of the diaphragm, a chamber arranged between the diaphragm and hydraulic working chamber, at least one overflow channel connecting the chamber with the hydraulic working chamber, a valve unit including a tappet with a valve disk at each end thereof facing openings of the at least one overflow channel into the chamber and hydraulic working chamber and movable alternately to close with one valve disk the opening into the chamber and with the other valve disk the opening into the hydraulic working chamber, and the valve unit being operatively connected with the diaphragm by means of a support disk and a light loading spring which urges the support disk into loose engagement with the diaphragm. 
     
     
       2. A diaphragm pump according to claim 1, wherein the spring is loaded such that, when hydraulic equilibrium exists on both sides of the diaphragm, the spring load merely overcomes inertia forces and frictional forces of the valve unit. 
     
     
       3. A diaphragm pump according to claim 1, wherein the support disk includes an elongated portion extending through the chamber. 
     
     
       4. A diaphragm pump according to claim 1, wherein an insert is provided between the chamber and the hydraulic working chamber, the at least one overflow channel being provided in the insert, and the tappet being guidably movable in the insert. 
     
     
       5. A diaphragm pump according to claim 4, wherein the insert contains a plurality of overflow channels surrounding the tappet, the channels having openings on sides of the insert facing the chamber and the hydraulic working chamber adapted to be alternately closed with the valve disks of the valve unit. 
     
     
       6. A diaphragm pump according to claim 5, wherein a bevel seat is provided at each of the sides of the insert facing the chamber and the hydraulic working chamber, each bevel seat having a small diameter approximating a diameter defined by an envelope of the openings of the overflow channels. 
     
     
       7. A diaphragm pump according to claim 6, wherein the valve disks are provided with a bevel face corresponding to the bevel seat of the insert. 
     
     
       8. A diaphragm pump according to claim 4, wherein the spring is arranged between the valve disks within the insert so as to have one end acting against the insert and the other end on the valve disk facing the diaphragm. 
     
     
       9. A diaphragm pump according to claim 1, wherein the spring is a helical spring supported at one end on the support disk and at the other end on a wall of the chamber opposite the support disk. 
     
     
       10. A diaphragm pump according to claim 1, wherein the diaphragm is made from plastic.